Temperature-regulating cabinet for photographic processing apparatus

ABSTRACT

A cabinet is designed to provide automatic temperature control for virtually any conventional, small scale photographic developing apparatus, and to rapidly adjust the temperature of all liquids to be used in conjunction therewith. Both these objectives are accomplished by use of a single liquidtemperature-sensing thermostat in cooperation with a heatingcooling air conditioning system; an array of individually removable, highly thermoconductive liquid-holding cells, and a compartment which receives a flow of tempered air from the spaces between the liquid-holding cells.

United States Patent Reichardt l TEMPERATURE-REGULATING CABINET FOR PHOTOGRAPHIC PROCESSING APPARATUS Theodore A. Reichardt, 8843 Mariposa St., La Mesa, Calif. 92041 Filed: June 20, 1973 Appl. No.: 371,746

Inventor:

US. Cl 354/299, 165/27, 312/236 Int. Cl. G03d 13/00 Field of Search 95/89 R, 94 R, 96, 93; 312/236; 165/27, 64; 354/297, 299, 307,

References Cited UNITED STATES PATENTS 11/1941 Lambrecht et a1 312/236 UX 4/1970 Weider et a1. 95/96 [4 1 Oct. 1, 1974 3,688,678 9/1972 Dalen l 95/96 3,695,162 10/1972 Wing 95/89 R 3,698,307 10/1972 Reichardt 95/93 Primary Examiner-Fred L. Braun 5 7 ABSTRACT 5 Claims, 8 Drawing Figures PATENTEBHUT H974 SHEET 1 0f 4 FIG. 2

PATENTEU BUT 1 7 FIG.

TEMPERATURE-REGULATING CABINET FOR PHOTOGRAPHIC PROCESSING APPARATUS CROSS REFERENCES TO RELATED APPLICATIONS Application Ser. No. 116,870., filed 19 Feb. 1971, now US. Pat. No. 3,698,307., by the same inventor, has some objects similar to those of this application, and discloses certain similar details.

BACKGROUND OF THE INVENTION This device relates to devices for temperature regulation of a confined space and particularly to such regulation using a current of temperature-regulated air as the medium of heat interchange. This invention is specifically directed to the provision of such an enclosure which can be adapted for use as a photographic processing machine and for storage of processing liquids.

Most existing equipment used for small-scale chemical processing, particularly equipment used in such processing of sensitized photographic films and papers, requires some form of temperature control if optimum results are to be obtained.

The most usual method of providing such temperature control is to provide a sink-type container partially filled with water, in which various types of processing tanks, trays, etc. may be submersed or partially submersed. Temperature control of the chemical process is achieved by maintaining the temperature of the water in the sink-type container at the desired processing temperature.

This is done either manually, by the occasional addition of a suitable quantity of hot or cold water, or auto matically by providing a steady flow of thermostatically controlled water into and out of the sink.

The first of these methods is obviously cumbersome, requiring considerable attention, and the second method is quite expensive, both initially and in operation, especially if both heating and cooling means are to be provided.

Methods involving the use of heated and cooled air to achieve the necessary temperature control have been largely ignored, mainly due to the slowness of heat transfer inherent in such methods. However to cite an example in which air temperature control has been used in a machine designed specifically for photographic processing, reference is made to the Photographic Print and Film Processing Machine or US. Pat. No. 3,698,307, held by-the same inventor.

In the latter case, thermostatic control is applied directly to a flow of air. This arrangement makes it possible to set and maintain a desired air temperature within the enclosure, thus insuring that containers of liquid, as well as and including the processing drum, would be maintained at the required temperature. This arrangement does not, however, allow either hot or cold air to flow steadily until the liquids in the containers reach the temperature which has been set on the thermostat. Thus the temperature control system of US. Pat. No. 3,698,307 provides efficient temperature maintenance for both liquids and processing drum, but lacks efficiency in quickly raising or lowering the temperature of a supply of liquids.

Other, somewhat similar machines have applied various temperature controlling means to specific, essen- 2 tially fixed equipment, whereas the present temperature regulating cabinet provides for the utilization of virtually all types of otherwise nontemperaturecontrolled equipment interchangeably, with uniquely simple and efficient heating and cooling temperature control both for the equipment and for liquids to be used in conjunction with the equipment.

SUMMARY OF THE INVENTION The present invention is designed to regulate and control the temperature of a quantity of liquids, while at the same time regulating and controlling the air tem perature within a compartment into which various types of chemical processing equipment, including photographic processing equipment such as tanks, drums and motion producing equipment may be placed interchangeably.

In the temperature regulating cabinet of this invention, tempered air is caused to flow first through the spaces between a series of adjacent, wafer-shaped liquid containers or cells and then into and through a processing compartment.

The cells are so constructed as to present a large surface area per unit'volume of contained liquid, and in the described embodiment are of a thin, translucent plastic material with textured sides, thus insuring efficient air-to-liquid, liquid-.to-air heat transfer utilizing both conductive and (by virtue of their translucency) radiative effects.

In order to heat or cool the contained liquids, tempered air is provided alternatively by a heater-blower and a blower fed by a cold-air source. A pipe-like container is provided which may be attached to the inlet of the cold-air blower, and into which ice cubes or other similarly embodied cold substance may be placed to cool the air which is drawn into the cabinet by the coldair blower. The pipe-like container may, however, easily be detached, allowing the cold air blower to be connected to any other cold air source such as an electrical refrigerating unit, or even to an outside wall vent if the outside air temperature is lower than contemplated processing temperatures.

Temperature selection is accomplished by means of a settable, heating-cooling thermostat, the sensing probe of which is submersed in the liquid in one of the identical, wafer-shaped containers. In order that the temperaturearegulative means shall produce practically identical results with respect to each of the liquidholding cells, it is only necessary that each cell (including the control cell which contains the thermostat probe) be initially filled to the same level, and that all liquids used for filling the cells be at essentially the same initial temperature, room temperature usually being convenient, and tap water temperature being a convenient alternative choice.

A fast, simple method of filling the cells is to have a supply of the necessary chemicals and/or water stored on a shelf above the machine, in containers bearing flexible hoses which may be directed into the cells through openings 67 without removing the cells from the cabinet.

One object of this invention is to provide, in a rela tively small machine, means for quickly heating or cooling a substantial amount of liquid chemicals and/or water without the need for a supply of flowing, temmethods.

Another object of this invention is automatically to maintain the temperature of a quantity of liquids within a range suitable for any ordinary photographic process, and most other moderate-temperature. chemical processes.

Another object of this invention is to provide a temperature controlled environment in which various chemical processes may be carried out, with temperature control sufficiently precise for any ordinary photographic process and for most other moderatetemperature chemical processes.

Another object of this invention is to provide means whereby a single temperature regulating system may be utilized in a dual manner; first to heat or cool a supply of liquids while at the same time moderating the temperature of air in a compartment, and secondly to then maintain the temperature of both the liquids, and the air in the compartment, at the same preselected temperature automatically.

In the present machine, the efficacy of heat transfer between liquid-holding cells and flowing air is such that the temperature of the air in the equipment compartment, if relatively high initially, will actually fall toward the set temperature when hot air begins to flow through the spaces between the liquid-holding cells the reverse is true of course when liquids are to be cooled.

In other cases, (when air temperature in the equipment compartment is initially quite close to the set temperature) a slight deviation away from the set temperature will be noted temporarily, until the temperature of the liquid in the cells reaches the set temperature, at which time this temporary deviation will be reversed and the equipment compartment will quite rapidly normalize to the set temperature.

A fine-reading thermometer of any convenient type may be placed in the equipment compartment to ascertain the above events.

Temperature regulation of the equipment compartment is achieved by causing the flowing air to pass directly into and through that compartment as the air exhausts from the spaces between the liquid-holding containers. The effectiveness of the above method is easily understood when it is realized that the average temperature of a series of samples of the air exhausting from the spaces between the cells becomes virtually identical with the temperature of the liquid in the cells once the contained liquids have attained the temperature set on the thermostat; at this point, the thermostat requisitions only a small net heating effect or a small net cooling effect to compensate for radiative gains or losses, such gains or losses applying nearly equally to both liquids and equipment.

The placement of various types of equipment into the equipment compartment (and removal therefrom) is accomplished by means of a hinged cover, which should be at least partially transparent for observation of events within. In the present machine this hinged cover bears a series of perforations for the exhaust of air flowing from the cabinet.

Cradle rollers and other electrically powered equipment may be operated in the equipment compartment without danger of motor overheating, because any heat produced by equipment motors is quickly carried out of the cabinet by flowing air of moderate temperature.

3 One of the advantages of this apparatus is that, in the case of photographic processing for example, virtually any type of easily obtainable processing equipment may be operated within the cabinet to take advantage of the controlled environment in the equipment compartment; such equipment encompasses, for example, stainless steel or plastic film developing tanks with or without cradle rollers or other motion-producing means; vertical standing film developing tanks with agitator handles, which may protrude through apertures provided therefor in the top cover of the cabinet; print developing drums with cradle roller means; sheet film tanks which may be agitated by auxiliary mechanical means, or by hand simply by lifting the top cover of the cabinet for a few seconds periodically, and virtually any other type of compatibly sized photographic processing devices in the use of which automatic temperature control would be advantageous.

Another advantage of this appararatus is that, after chemical processing films on reels, sheet films on hangers, and even prints on ferrotype plates may be placed in the equipment compartment forair drying at any suitable temperature, simply by setting the thermostat for the desired temperature. An air filter may be fitted into the cabinet just below the equipment compartment to remove dust from the air used for drying.

Another advantage of this apparatus is that a cabinet of a given size, for example a cabinet large enough to accomodate a drum and cradle roller for processing 16 by 20 inch prints, may also be used, with equal effectiveness, to contain and control the temperature of any smaller sized equipment, such as a tank for developing a single roll of film.

Another advantage of this apparatus is that the use of tempered air to regulate the temperature of liquids and equipment insures that the operators hands, as well as the exterior surfaces of processing tanks and the like, may remain dry at all times. This eliminates much of the inconvenience encountered in water-bath temperature control methods. This advantage is notably important in the case of photographic processing, where dry sensitized materials must be handled periodically.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a front elevation, partly broken away, of the temperature-regulating cabinet.

FIG. 2 is an elevation of one side of the cabinet.

FIG. 3 is a rear elevation of the cabinet.

FIG. 4 is an elevation of the side shown in FIG. 2, sectioned at 44, FIG. 1.

FIG. 5 is a schematic electrical diagram of the cabinet.

FIG. 6 is a front elevation of the thermostat.

FIG. 7 is a side elevation of the thermostat, sectioned at 77, FIG. 6.

FIG. 8 is an isometric view of one cell.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the figures, a cabinet 11 is provided with a hinged, transparent top 12, having the approximate form of a semi-cylinder. This tip is provided with a series of uniformly spaced holes 13 for the uniform exit of air. The front of the cabinet is provided with a transparent door 14, hinged at 16, and a snap fastener 17. The cabinet is divided generally into three parts. The upper part, 18, FIG. 4', is designed to contain equipment for the chemical processing of photographic materials, or to contain other apparatus for which temperature control is required or advantageous.

The middle part l9is filled with wafer-shaped cells, liquid-tight except for pouring and filling openings. The lowest part 21 is a plenum chamber. The three parts of the cabinet are separated by grills, 22 and 23, FIG. 4, allowing easy passage of air. Grill 23 is a series of identical front-to-rear slats for supporting the cells 24, FIG.

l, and for guiding their insertion into the cabinet. The width of these slats is slightly less than that of grooves in the bottoms of the cells. The slats and grooves thus guide the cells into position.

The cell space in the cabinet is provided with a rear wall on which there are positioned a row of shallow, vertical septums. These septums, along with the horizontal slats, define the position occupied by each cell so that there are equal spaces between the cells. A box 26 is secured to the rear side or wall 27 of the cabinet 11. The wall separating cabinet 11 from the box 26 is open below grill 23, this opening constituting an aperture joining the plenum chamber to the interior of the box 26.

The box 26 is provided with two means for forcing air into it. One means consists of an electric blower 28, with a self-contained heating element controlled by a switch 25. Blower 28 forces heated air through pipe 29 into box 26. The other means consists of a cold-air fan contained in shroud 31, positioned to draw air through a large pipe-like container 32, FIG. 2, and to deliver it through shroud 31 into the box 26. A flapper valve 33C, FIG. 4, hanging from a hinge 34 closes the opening of shroud 31 when the warm-air blower is operating. A second flapper valve, 33H, closes the hot air blower exit when the cold-air blower is operating. The function of pipe 32 is to hold a quantity of pieces of cold material such as ice cubes, so that air passing through the pipe will be cooled before it is conducted into shroud 31. The pipe 32 is removable and the shroud 31 may be-connected by a duct to any other cold air source, such as an ordinary room air conditioner. An electrical outlet 35 is provided for such an alternative cold air source, and is connected in parallel with the cold air fan so that both the cold air fan and the alternative cold air source may operate automatically according to the thermostat setting.

A switch 36, FIGS. 2 and 5, is provided to control the power to the temperature control system. The position of switch 37 determines whether the heating fan or the cooling fan shall operate initially, to achieve a temperature as set on the thermostat 38 and is therefore a double-pole, double-throw switch marked HEAT and COOL. After the settemperature is reached with respect to the liquid in the cells, the thermostat, acting through a double pole, double throw relay 39, causes the heating fan and the cooling fan to operate alternately as required to maintain the set temperature.

When operating at temperatures at least a few degrees above room temperature, the cold air fan need not be provided with any cold air source, and simply draws room air into the cabinet as required according to the action of the thermostat.

Another method of utilizing an ordinary room air conditioner or similar machine with this apparatus is to use it as a heat pump, with ducts to the box 26 from both the cold air discharge and the hot air discharge. In this arrangement, both the hot air fan 28 and the cold air fan 30 may be eliminated, while the action of the double pole double throw'relay 39 may be employed to energize a pair of solenoid-operated air valves (each with interdependent by pass valve) to control the passage of hot and cold air into the box 26 according to the action of the thermostat.

The thermostat 38 is shown enlarged in FIGS. 6 and 7. It consists of a dial-type thermometer 40 and cooperating parts as will be described. The stem 41 of the thermometer 40, containing the sensing mechanism, projects through an opening in the top of a centrally positioned liquid-holding cell 42, which serves as a control cell when all the cells are filled to the same level with liquids of the same temperature.

The thermometer 40 is protected by a removable cover 43, having an opening 44. The thermometer dial frame 45 projects through this opening, and can be turned by hand to rotate the thermometer. This dial frame carries a circular scale 46, marked in degrees Fahrenheit, for setting the thermostat to a desired operating temperature. An index plate 47, secured to the cover 43, is provided to read the scale 46. The plate 47 is provided with two index points marked C and H for COOL and HEAT respectively. These two index points are separated by a distance equal to the effective width of a mask attached to the pointing hand 48 of the thermometer 40 as will be described.

To the thermometer hand 48 there is secured a fine, stiff wire 49. This wire, on its opposite end, carries an opaque mask 50, firmly secured to the wire. The opposite end of the hand 48 is provided with a weight 51 to counterbalancethe weight of the wire 49 and the mask 50. A small lamp 52 and a photocell 53, supported by its lead wires 54 are positioned so that the lamp and the photocell are aligned and so that the mask can move, as occasioned by the motion of the hand 48, either to cutoff the lamplight falling on the photocell or to allow the light to reach the photocell. The thermostat lamp 52, being of low voltage, is fed, through a transformer 56, from the electric power source. The output potential of the photocell 53 is applied, through an isolation relay 55, to DPDT relay 39. The heating element of the heater-blower 28 is of relatively low wattage, as its function is primarily to maintain a set temperature by replacing heat lost from the cabinet to the external environment.

In order to increase the available amount of heat for quickly heating a supply of liquids, without raising the temperature within box 26 to an unacceptable level, a double, auxiliary heating element 58 is positioned in proximity to the liquid holding cells, in the plenum chamber 21. Thus the liquid in the cells may be rapidly brought to a higher temperature by energizing, initially, both the heater blower 28 and the auxiliary heating element 58. However, for economy of operation, the auxiliary heating element 58 may be turned off when no longer required. A reflective material may be positioned beneath the auxiliary heating element 58 to increase its effectiveness in heating the liquids. Auxiliary heating element 58 is constructed so that its output diminishes slightly toward the center of the cabinet, and increases slightly toward the sides of the cabinet, in order that each cell shall receive nearly the same amount of heat from that source.

Auxiliary heating element 58 is of liquid-safe construction, for example, similar to the type used in cooking ranges.

If the present machine is to be constructed on a relatively large scale, requiring that the liquid-holding containers be filled with rather large amounts of liquid, a series of individual, wafer shaped heating elements 59, FIG. 1, may be interposed between the cells 24, either replacing heating element 58 or in addition to it. If the heaters 59 are to be used, the liquid-holding containers must of course be constructed of material which can withstand the direct application of a considerable amount of heat, as well as being suitable for contact with whatever liquids are to be contained.

A rheostat/switch 61 turns on the auxiliary heat source and determines its operating level. The rheostat should be calibrated in terms of the difference between present liquid temperature and desired liquid temperature, and should be set to indicate this difference in order that heat shall be applied at an optimum rate rather than at a rate which would allow too much heat to reach the equipment compartment during the time that heat is being applied continuously.

By proper calibration and proper setting of the rheostat as described above, the temperature of the air in the equipment compartment will not rise significantly during the heating phase (and will in some cases actually drop slightly at first), and will normalize to the set temperature very quickly after the liquid in the containers reaches the set temperature.

A switch 62, FIG. 2, is provided to control, through outlet 63, electrical energy supplied to equipment contained in the compartment 18.

FIG. 8 depicts the type of cell shown at 24, FIG. 1. The cell top 64 is open at the rear corner 66 and at the cut-off front corner 67, otherwise the cell is liquidtight. The open front cut-off corner 67 provides access to the interior of the cell for filling when in place in the cabinet, and the rear top opening provides a spout for pouring liquid from the cell. The bottom of the cell is provided with a slot or groove 68 slightly wider than the slats composing the grill 23, each slot and slat serving as a runway to guide a cell into place.

While the sides of the cell of FIG. 8 may be of a metal such as stainless steel for liquid chemicals, or aluminum for those cells which are to contain water, various plastic materials may also be used and have been found to be highly thermoconductive when the plastic is translucent and of textured exterior surface.

The narrow front wall of at least one of the cells should be of a transparent material, in order that a finereading capillary-tube thermometer 71 may be permanently positioned in the cell and easily read through the transparent front door of the cabinet and the transparent front wall of the cell. With such a thermometer in place, very fine adjustments may be made to the setting of the thermostat to obtain extremely accurate temperature control where required, such as in the case of color developer solutions in photographic processing.

The cell 42, at the center of the array, filled with water, serves as the control cell and contains the sensing stem 41 of the thermostat 38. The control cell may also contain the thermometer 71, or the latter may be positioned in a nearby cell, such as a cell containing developing liquid.

1n the operation of the temperature-regulating cabinet, the cells are filled as described and the processing equipment is placed in compartment 18. if the processing equipment to be used is power-operated, its power cord is connected to the electrical supply through switch 62 and outlet 63. There are then two possible conditions of use, as follows:

Condition 1. Required processing temperature is higher by at least several degress Fahrenheit than present liquid temperature, as shown by thermometer 71.

Procedure:

1. Set desired temperature on thermostat.

2. Set DPDT switch 37 to HEAT, and switch 25 to LGONIQY 3. If maximum rate of heating is desired, set rheostat/switch 61 to indicate number of degrees of required temperature rise, thereby activating auxiliary heating means and allowing it to produce heat at the maximum permissible rate.

4. Turn switch 36 to ON.

5. When the set temperature is reached, rheostat/- switch 61 may be turned off. (However if this is not done, the only effects will be somewhat faster cycling of the temperature control system and slightly greater current consumption).

Results:

When set temperature is reached, the mask interrupts the light beam; isolation relay becomes normal, opening its contacts; DPDT relay 39 becomes normal; potential to hot air blower 28 is interrupted and potential is applied to the cold-air fan 30. When the thermostat senses a slight drop in temperature, the light beam again strikes the photocell 53; the cold air blower 30 is cut off and the hot air blower 28 is turned on. Thus the system oscillates between (1) the heaterblower and (2) the cold air blower which draws either cooled air or ambient room air into the cabinet according to the circumstances mentioned above. By this action, the liquids in the containers and the air in the equipment compartment are maintained at nearly exactly the set temperature. In one example, the temperature differential experienced by the liquids in the cells, and by liquids contained in apparatus in the equipment compartment, is less than /z Fahrenheit. Even greater accuracy (smaller differential) may be obtained by constructing the thermostat so that a smaller rotation of the hand 48 controls passage of the light beam to the photocell 53. This may be done by several obvious means, for example increasing the length of the wire 49 which supports the mask 50. 3 Condition 2. Required processing temperature is lower than, or very close to present liquid temperature. Procedure:

1. Set desired temperature on thermostat.

2. Set DPDT Switch to COOL," and switch 25 to 3. Place a quantity of ice in the pipe, 32, or provide alternative cold air source as previously described.

4. Turn switch 36 to ON" position. Results:

Light beam of lamp 52 strikes photocell 53; isolation relay 55 closes its contacts; DPDT relay 39 operates; potential is applied to the cold air blower 30. When the set temperature is reached, the mask 50 interrupts the light beam, isolation relay 55 and relay 37 become normal, potential to cold-air blower 30 is interrupted and potential is applied to the hot-air blower 28. When the thermostat senses a slight rise in liquid temperature in the control cell, the light beam again strikes the photocell 53, the hot air blower is automatically de-energized and the cold-air blower is automatically re-energized. Again the system oscillates, exactly as described under fCondition 1, except that passage of the light beam to the photocell 53 is controlled by the opposite edge of the mask 50.

I claim:

1. In a temperature regulating cabinet, the combination of:

a cabinet having a lower compartment, a central compartment and an upper compartment, and having at least one access to said central compartment and at least one access to said upper compartment;

a first open grillwork-type floor, partitioning said lower compartment from said said central compartment, and disposed to support in said central compartment an array of closely spaced, highly thermoconductive liquid-holding cells;

first means in said central compartment to engage and hold in vertical stance each of said liquidholding cells;

a second open grillwork-type floor, partitioning said {central compartment from said upper compartment, and disposed to support, in said upper compartment, at least one container in which chemical reactions may take place;

second means for heating air;

third means for cooling air;

fourth means for propelling air from said second means and said third means, alternatively, into said lower compartment, thence through said first open grillwork-type floor, between and around said liquid-holding cells, through said second open grillwork-type floor, and into said upper compartment;

at least one aperture in said upper compartment to allow air to escape therefrom;

a settable, heating-cooling thermostat, disposed (l) to sense directly the temperature of a liquid in one of said liquid-holding cells and (2) to activate, accordlngly, either said heating means or said cooling means continuously until the temperature of said liquid is in agreement with the setting of said thermostat; and

liquid temperature differential limiting means, comprising automatic switch means to quickly activate said cooling means whenever said heating means is deactivated in response to the sensing of said thermostat, and to quickly activate said heating means whenever said cooling means is deactivated in response to the sensing of said thermostat.

2. A temperature regulating cabinet in accordance with claim 1, wherein said second open grillwork-type floor may also support at least one conventional apparatus normally used to cause liquid in a container to be agitated.

3. A temperature regulating cabinet in accordance with claim 1, wherein said container in which chemical reactions may take place comprehends at least one conventional photographic developing container.

4. A temperature regulating cabinet in accordance with claim 1, wherein said first means consists of a row of shallow, vertical septums at the rear of said central compartment.

5. A temperature regulating cabinet in accordance with claim I, wherein said cells are grooved along their narrow bottom sides, and in which said first open grillwork-type floor comprehends a row of slats, whereby the cooperation of said grooves and said slats regulates the separation of said cells from one another and guides said cells into engagement with said first means. 

1. In a temperature regulating cabinet, the combination of: a cabinet having a lower compartment, a central compartment and an upper compartment, and having at least one access to said central compartment and at least one access to said upper compartment; a first open grillwork-type floor, partitioning said lower compartment from said said central compartment, and disposed to support in said central compartment an array of closely spaced, highly thermoconductive liquid-holding cells; first means in said central compartment to engage and hold in vertical stance each of said liquid-holding cells; a second open grillwork-type floor, partitioning said central compartment from said upper compartment, and disposed to support, in said upper compartment, at least one container in which chemical reactions may take place; second means for heating air; third means for cooling air; fourth means for propelling air from said second means and said third means, alternatively, into said lower compartment, thence through said first open grillwork-type floor, between and around said liquid-holding cells, through said second open grillwork-type floor, and into said upper compartment; at least one aperture in said upper compartment to allow air to escape therefrom; a settable, heating-cooling thermostat, disposed (1) to sense directly the temperature of a liquid in one of said liquidholding cells and (2) to activate, accordingly, either said heating means or said cooling means continuously until the temperature of said liquid is in agreement with the setting of said thermostat; and liquid temperature differential limiting means, comprising automatic switch means to quickly activate said cooling means whenever said heating means is deactivated in response to the sensing of said thermostat, and to quickly activate said heating means whenever said cooling means is deactivated in response to the sensing of said thermostat.
 2. A temperature regulating cabinet in accordance with claim 1, wherein said second open grillwork-type floor may also support at least one conventional apparatus normally used to cause liquid in a container to be agitated.
 3. A temperature regulating cabinet in accordance with claim 1, wherein said container in which chemical reactions may take place comprehends at least one conventional photographic developing container.
 4. A temperature regulating cabinet in accordance with claim 1, wherein said first means consists of a row of shallow, vertical septums at the rear of said central compartment.
 5. A temperature regulating cabinet in accordance with claim 1, wherein said cells are grooved along their narrow bottom sides, and in which said first open grillwork-type floor comprehends a row of slats, whereby the cooperation of said grooves and said slats regulates the separation of said cells from one another and guides said cells into engagement with said first means. 